A team of Dexon pipeline engineers recently completed the inspection of a 32km, 3” underground petrochemical distribution pipeline running from an onshore processing facility to a port on the South American coast that was characterized as challenging or “unpiggable.” This was the first inspection for this pipeline in its 30-year life due to the difficult nature of the inspection. The small diameter of the pipeline meant that specialized tool development, modification and testing were required at Dexon’s headquarters in Thailand prior to the inspection, with onsite client verification performed in early December 2022.

The Challenge

• 3” small-diameter inspection of a long-range 32 km distribution pipeline (typical 3” transfer lines run for only a few hundred meters in a single plant).
• Pipeline characteristics, such as weld penetration that can cause significant internal diameter restrictions in small-diameter pipelines.
• Lack of previous inspection data, with this being the first inspection for this pipeline.
• Online inspection.

The small diameter of the pipeline paired with the long inspection length of 32km made this inspection challenging. Typical 3” transfer pipelines run for a few hundred (200 to 400) meters within a single plant, making this run 106 times longer than a typical 3” inspection run. While weld penetration and other characteristics in such small-diameter pipelines can cause significant reductions in the pipeline’s internal diameter, the limited space inside the tool bodies caused by the small diameter of the pipe required customized design, modification and testing of the tool prior to the inspection. Providing sufficient battery life and data storage to complete the inspection was also crucial. In addition, this was the first inspection for this pipeline in its 30-year lifetime, causing uncertainty around the geometric condition of the pipeline in underground sections that could possibly lead to a stall. The client required the inspection to be completed online, reducing the impact on operations.

The Solution

• Customized design and modification of Dexon Technology’s existing 3” small diameter UT-MC fleet.
• Customization of Dexon’s onsite test loop configurations to replicate inspection conditions.
• Extensive long-range durability testing at Dexon’s onsite test yard.
• Onsite client inspection data verification.
• Comprehensive cleaning and gauging to adequately gauge the geometric condition of the pipeline prior to inspection.

Dexon Technology’s Research, Development and Engineering department offers customized tools developed as part of Dexon’s Challenging or “Unpiggable” Pipeline Inspection Program. A pipeline inspection gadget (PIG) from Dexon’s existing 3” UT-MC fleet was modified to complete the inspection, providing additional battery units to accommodate the long operating time of the inspection. The PIG traveled at approximately 1 m/s over the 32km distance, for a total inspection time of 9 hours from launching to receiving. Dexon Mechanical Solutions (DMS) (Dexon’s pipeline maintenance and repair division) performed alterations to Dexon’s onsite test loop configurations to replicate inspection conditions and allow for extensive long-range durability testing prior to the inspection. Onsite client inspection data verification was performed in early December 2022, with a team of pipeline operators visiting Dexon’s headquarters in Thailand. A thorough cleaning and gauging were performed onsite to adequately determine the geometric condition of the pipeline and avoid a stall in the line.